解決Skipped loading plugin with error: XML Document '/opt/ros/melodic/share/rqt_virtual_joy/plugin.xml' has no Root Element的問題

1、在ROS官網找到rqt_virtual_joy/plugin.xml，復制文件內容

<library path="src">
  <class name="My Plugin" type="rqt_virtual_joy.virtual_joy_module.MyPlugin" base_class_type="rqt_gui_py::Plugin">
    <description>
      An example Python GUI plugin to create a great user interface.
    </description>
    <qtgui>

      <group>
        <label>Robot Tools</label>
      </group>
      <!-- <group>
        <label>Subgroup</label>
      </group> -->

      <label>Virtual Joystick</label>
      <icon type="file">resource/input-gaming.png</icon>
      <statustip>Great user interface to provide real value.</statustip>
    </qtgui>
  </class>
</library>

2.打開報錯中指出的文件缺失的目錄/opt/ros/melodic/share/rqt_virtual_joy/，新建文件plugin.xml

3.打開plugin.xml，粘貼第一步復制的代碼，保存退出即可。

參考;https://answers.ros.org/question/354039/rqt_virtual_joypluginxml-file-is-missing/